BITSAT Chemistry Question (2024) — Solution

Step-by-step solution

(a) Ni in [ Ni ( Cl )_4 ]^ 2- exist as Ni ^ 2+ ion. Cl is a weak field ligand (high spin). It will not cause pairing of electrons. Hence, configuration of [ Ni ( Cl )_4 ]^ 2- is Tetrahedral with two unpaired electrons (i.e., paramagnetic) and has s p^3 hybridisation. (b) In [ Co ( C _2 O _4 )_3 ]^ 3- , ( C _2 O _4 )_3^ 2- is a bidentate ligand thus, give octahedral structure. (c) In [ Ni ( CN )_4 ]^ 2- , Ni exist as Ni ^ 2+ ion. CN ^ - is a strong field ligand (low spin). Causes pairing of electrons of 3 d orbital. Hence, the structure of is square planar and it is diamagnetic. (d) In [ Ni ( CO )_4 ], Ni has zero oxidation state. i.e., CO is a strong field ligand causes rearrangement and pairing of electrons of 3 d and 4 s orbital. Structure of Ni ( CO _4 ) is tetrahedral with s p^3 hybridisation and it is diamagnetic. Hence, (4) is the correct answer.